Smelting tin and other ores



J. H. GRAY.

SMELTING TIN AND 0THER ORES.

APPLICATION FILED MAR. I8. 1919. v

Patented May 25,1920. I

(SHEETS-SHEE I.

lwmron -Jame5/ifiray I BY /MM man/15f GRAY.

, APPLICATION FILED MAR. 18, I919- 1,340,95 1 Patented May 25, 1920.

4 SHEETSSHEET 2.

J. H. GRAY.

SMELUNG TIN AND OTHER ORES. APPLICATION FILED MAR. 18, 1919.

"1,340,951, r Patented May 25,1920.

4 SHEETSSHEET 4.

IN VEN TOR Jam; H [fizzy Mk ATTORNEY BX56, 012? 333W YORK. 3. fiIvZIQZLTIFJlG TEN AND (Ti-33$.

k elii' h rin Specification of Letters Eatent, ifliQ-lgijijfi 31 25 1192'}, Application filed Bilaech 18, 1919. Serial No. 283,303.

1 '0 all whom only concern Be it lumen that i, JAMES Unix, a citizen of Lllll United nabs. suhno in Tin a mi other fires, olhm a soecihcation.

c i in the smelting; oi' tin the ore is usually placed with the ncmssary iillBiQS on the hearth of a 101' reverheratory ii'urnace which he: .cd by means of a. flame passing other. The (lame is re not most e'ilective from the on. which Also a. certain amount of tin is volaf lined mull carried l the 1 ft into the Ll. n 1; lues or into the atmosphere. A part or this is lost and part it is recovered, though with (liiiiculti' and at considerable expense. Similar (iiiii iltles; are met in the smelting oi ores oi other motels which are easily latilize l, such for example as zinc. Other styles of furnace ha 'e been proposed but have not superseded that above described.

I propose to heat the ore electrically oy a very efiic cnt resistor and to maintain the atmosphere and all the conditions neutral 0 at least non-oxidizin within the 'lin'nace; which is specially axlayted for he purpose of smeltingsuch ores and which may also be usecl for a number oi other purposes. Other features of advantage have also been incor 'iorztted, as stated in detail he enaiter.

The aceonipanyiiw drawings iilustrate such furnaces and their method use.

Figure l. is a cent ill vertical section;

Fig. 2 is a. horizontal section through the charging doors;

Figs. 3 and 4 are partial vertical sections through the metal tapping and slag tapping (memo rs respectively;

Fig. 5 isa diagrammatic plan trical connections;

Fi 6 zunl "Z are a i liagraminatic plan :zuil section respectively, illustrating a modil. from one end to the oxidizing anal is the in eliminating usually of the elecof the furnace Referring to the example illustrated in Fig. l. the well *2 is circulan which colic or equivalent confluctive material 5" may be ii'itroducefl and which (luring operation is practically closed by a stopper 6. The coke falls into a well 7 locetecl at the center of the hearth of the furnace and forms a mound. lietwecn azul erouinl the lower ends of the electrodes, iJQ- ing preferably introduced in suilicient quantity to fill the well and to cover the side Walls thereof. This well formed in a central memher 8 which has an opening at the bottom closed hy a plug 3 which can he .vit-hah'au'u in order to permit ren'xowl or the ash which gradually accumulates as the coke is consumed.

Around the -ntral member 8 is an annnler hearth i shaped to form an annular trough il in which the ore is placed and reduced. 'llurrent is conveyed to the separate electrodes by cables 12 and they are supported from (Warhead in any usual or suit able Way and gradually lowered as they are consumed. hen the current is applied the coke becomes incamlcsccnt, small arcs luring formed between the pieces of the colic in the path of the current as it )2 sses from one electrode to another. The tei'npcraturc which can he ohteinml in this way VCI'Y great. The temperature of the electric ai c is one of the highest known, namely 1 600 (icgrecs ccntigrznle, aiul the coke can he nnulo to )roech this temperature if desired hv the use oi: very heavy electric currents. The heat from the central portion of the furnace radiates out over the charge and causes the desired reaction hetween the .xygen oi the ore and the carhon which mixed therewith in the Pharge and thus lilu'arates the tin. The

gases formed in the ii urnfu'ie are mainly carbon monoxhl, which is reducing oat least moi-oxidizing. i he formation. of: gases within the "Furnace causes 2. pressure therein which ordinarily prevents air from entering. lint when the (lOOlS of the furnace are opened ior charging or for manipulating" the charge on the hearth a certain quanti of air enters and unites; with the iiiraiulescent coke in the center, which is then gradually c nsuniesl. Additional coke is introduced from time to time as neealeil through the opening 5 in the roof of the l l urn annular hearth '11 will .7 i name :1. lor e29 tons of tin or tin and anal pining containing 89% of tin oxid and 11% of impurities (largely silica and partly lime and alumina) to which are added one and the furnace which may be used for charging the furnace or for 'abbling or manipulating the charge. Or charging openings 13' (Fig. 1) may be made in. the roof and will facilitate mechanical charging, and should be provided with close fitting plugs or covers. For drawing off the molten tin there are tapping holes 1% (Fig. registering with the bottom of the annular trough l1 and provided with spouts 15 for convey-- ing the tin into a vessel 16. For removing the slag from time to time there are openings l7 (Fig.4) registering with the slag level and spouts 18 for running the slag oil into suitable vessels 19.

During the smelting operation a certain amount of. the coke in the central well may flow over the wall thereof, but no harm will be done because it will enter the slag on the charge and merely increase the reducing agent therein. It is advisable to keep the wall of the center well covered with coke so as to protect it from the heat. Likewise no harm will be done if, during the boiling of the charge, some of the slag therefrom-should overflow the wall and mingle with the central mass of coke. The slag at high temperatures is electrically conductive and will serve like the coke as a heating medium.

I prefer a mound of colre as described,

but the conductive material in the well may consistof other substances and the surface of the mass may be horizontal instead of convex as shown. In the case of such a horizontal massthe electrodes will not be buried therein but visible arcs will be struck between the electrodes and the beating medium. This arrangement works well-in supplying heat for smelting, but the exposed arcs are more destructive to the refractory material used in the construction of the furnace. It would be possible, for instance, to haie the central well filled with pig iron which will be molten during the operation of the furnace, or the pig iron might be covered with a slag which would be conductive at high temperatures.

The sides of the central well should be made of a good refractory material such as magnesia brick and l have assumed that the central member 8 is all madeof such brick, or the bottom and sides of the central well may be made of carbon. The member 10, however, in which the annular trough ll is formed may be of less refractory material volt changer.

The wires constituting the line 20 pass through oil switches 21 to successive points in the primary coils of a transformer 22 of which the secondaries are connected by bus bars 23 to the cables 12 which lead to-the, several electrodes. As the current is passed,

through one or another-of the switches 21 the number of turns of the primary coils of the transformer which remain in the circuit is increased or decreased similarly changed.

When the current is first applied the voltage may be between one and two hundred for the design of furnace shown, say approximately one hundred and fifty volts.

The current flowing is indicated by am-f meters and gradually increases in quantity as the resistor .is heated. The voltage is, therefore, gradually cut down by means of the volt changer described t6 say between thirty and'forty volts. By this means the temperature of the furnace can be controlled.

' Before introducing the charge I prefer to heat the resistor and to cut the voltage down to. a point where a moderate temperature is secured, bringing the temperature in the whole furnace to something less than that which is required during the smelting operation. I then introduce the charge, say of tin ore, carbon and fluxing materials above described, and after it has become heated and. has been worked in the usual Way I increase the current and raise the temperature. Supposing that. in the design illustrated the electrodes are twenty-four inches in diameter, I propose to use 2000 K V A in the furnace and this will give a temperature of approximately 1600 degrees centigrade. At the usual or appropriate times slag is withdrawn. After about sevenhours the whole charge is reduced and the tin is in a molten form on the bottom of the annular trough, and is withdrawn through the tap holes-provided for the purpose. The.

bottom of the furnace is then repaired if and the voltage necessary and a new charge is immediately introduced and treated as before.

In order to allow gases to escape from the furnace freely but without admission of air and at the same time to trap any tin whichmay he in the gases in the form of 011d, 1 provide fines 24 communicating with mcewun me bottoms sf these fines .t wins-m1. and inzhmye mating 90 Closed 1t; .11 z

i131 embodiments B.

mm oxid iz- Said mn'u *1 .011, it will ba: 1111- tne (.1051

whici -abumiied.

The

Lem $1 0111 1 3.9 covers baa 01 "*he central my be usm sur ed:

movab shown is 17m". 1

(fixing mans to form *fillill to receive and carry a body of resistant materiel adapted to be heated by surreal: from said electrodes.

6. A furnace adapted for smelting ores of low volatile metals and for melgihg such metals having a reef, a set of GleCilUdQS depending' *lhi'oug li the roof and forming a cage to receive and carry a body of i'esistans material the roof having an opening vthrough which the resist ant material can he 9. The method. of providing heat for smelting ores of low Volatile melals and for meltingsuch mesals which consists in arranging electrodes in she form of a cage, introducing a body of resistant material into said cage and heating said body by currene from said electrodes.

10. The method of smelting ores of low volatile mehals and melting such metals which consists in provicling electric; he m ing device and ai'rengzng the chaige on and cutsiale of the same.

hearth surrcui'icling 11. The method of smelting ores of low volatile metals which consists them in a furnace by means of an electric heating (levice comprising a i'esisior, *arapping the fumes in a body-of resistant; mate iriah and using such material as the resistant medium of the i'esisiei'.

In witness whereof I have hereunto signed my name.

in heatm 

